1. Field of the Invention
The present invention relates to a semiconductor device and a method for manufacturing the same, particularly to the structure of a connection hole in which a second electrically conductive layer is embedded for electric connecting a first electrically conductive layer and the second electrically conductive layer with an insulating layer between them and to sputtering used for forming the embedded second electrically conductive layer.
2. Description of the Related Art
Recently, as a semiconductor element is miniaturized, the size of a connection hole formed through an insulating layer for electric connecting a first electrically conductive layer consisting of a conductive diffusion layer formed on one main surface of a semiconductor substrate or a metallic film formed on a semiconductor element and a second electrically conductive layer consisting of a metallic film formed on the insulating layer between both layers has been also miniaturized.
As the aspect ratio (a ratio of height of a connection hole to the diameter) of a connection hole is larger as the connection hole is miniaturized, electric connection between the first and second electrically conductive layers enabled by embedding the second electrically conductive layer in the above-described connection hole by keeping in ambient atmosphere of high temperature and pressure after a portion over a space is blocked by the second electrically conductive layer formed by sputtering with the space left inside the connection hole is discussed.
Referring to FIGS. 3, 5 and 38, a method for manufacturing a semiconductor device wherein a first electrically conductive layer formed on a semiconductor element and a second electrically conductive layer are electrically connected by embedding the second electrically conductive layer in the above-described connection hole by keeping in ambient atmosphere of high temperature and pressure after a portion over a space is blocked by the second electrically conductive layer formed by sputtering as described above with the space left inside the connection hole, for example a method disclosed in Published unexamined patent application No. Hei. 7-503,106 will be described below.
First, as shown in FIG. 35, a first electrically conductive layer 2 is formed on a semiconductor element 1, an insulating layer 3 is formed on the first electrically conductive layer and a connection hole 4 is formed through the insulating layer 3.
Next, as shown in FIG. 36, a second electrically conductive layer 6 is deposited on the above-described insulating layer 3 and inside the connection hole 4 by sputtering. At this time, as shown in FIG. 36, the second electrically conductive layer 6 deposited on a side wall 4a and the bottom 4b of the connection hole 4 is thinner than the second electrically conductive layer deposited on the insulating layer 3.
When the second electrically conductive layer 6 is further deposited by sputtering, a gap 7 between the second electrically conductive layers over the connection hole 4 is blocked with a space 8 left inside the connection hole 4 as shown in FIG. 37.
Next, the second electrically conductive layer 6 is embedded in the connection hole 4 by keeping in ambient atmosphere of high pressure until it is in a condition shown in FIG. 38.
As in the semiconductor device manufactured as described above, the second electrically conductive layer is embedded in the above-described connection hole 4 by applying high temperature and pressure after a portion over a space 8 is blocked by the second electrically conductive layer 6 formed by sputtering with the space 8 left inside the connection hole 4, the first electrically conductive layer 2 and the second electrically conductive layer 6 can be electrically connected via the connection hole 4.
However, in a method for manufacturing the semiconductor device constituted as described above wherein the second electrically conductive layer 6 is embedded in the above-described connection hole 4 by applying high temperature and pressure after a portion over a space 8 is blocked by the second electrically conductive layer 6 formed by sputtering with the space 8 left inside the connection hole 4, the thickness of the second electrically conductive layer 6 is required to be approximately twice as thick as the diameter of the connection hole 4, and it takes a long time to embed the second electrically conductive layer in the connection hole. A satisfactory characteristic of embedding the second electrically conductive layer 6 in the connection hole 4 cannot be obtained and therefore, stable electric characteristics and reliability can be hardly obtained.